1. Field of the Invention
This invention relates to novel siloxy substituted naphthalocyanines, and a process for their preparation. The present invention also relates to useful applications of the siloxy substituted naphthalocyanines, e.g., in the information layer of an optical information medium.
2. Description of the Prior Art
Optical recording methods in which light from a laser is focused upon the surface of a recording medium with sufficient intensity to cause a detectable change in the physical characteristics of the surface material have been proposed. Among these methods is the establishment of an information pattern of pits. In such methods, the information representative pattern of pits may be formed in the surface of the recording medium by suitably controlling the intensity of the focused light in accordance with the information to be recorded while relative motion is established between the recording medium and the focused light spot.
Organic materials have been employed as the recording layer for optical data storage media, as described by Kuder in the Journal of Imaging Technology, Vol. 12, No. 3, pp. 140-143. These are typically thin films comprising either a dye in a polymer matrix, or a dye only. Organic recording layers are often more sensitive to the write laser beam than metal films due both to lower melting or softening temperatures and to low thermoconductivity. While metal films are typically sensitive to a broad spectrum of wavelengths, dyes used in organic media are narrow absorbers that must be carefully chosen so that the absorption matches the laser wavelength employed for writing. This disadvantage has led to a search for chromophores useful in optical data storage media which are sensitive specific to laser wavelengths.
The use of organic materials such as phthalocyanine and naphthalocyanine chromophores in optical recording media is known to the art. For example, the use of phthalocyanine dyes in conjunction with optical recording media comprising a styrene oligomer is disclosed in an article by Kuroiwa et al appearing in the Japanese Journal of Applied Physics, Vol. 22, No. 2, February 1983, pp. 340-343. Among the dyes and pigments discussed as being useful is a copper phthalocyanine pigment. The phthalocyanine dye conferred sensitivity to the helium-neon laser beam employed for data storage.
Japanese Patent Application No. 57-173, 749, published Apr. 9, 1984, of Kuroiwa et al, discloses an optical recording medium having alleged improved sensitivity. The recording medium comprises a recording layer composed of a polymer having a phthalocyanine residual group as a side chain.
Other publications which discuss the usefulness of various phthalocyanine chromophores in the recording layer optical information media include U.S. Pat. Nos. 4,241,355; 4,298,971; 4,458,004 and 4,529,688.
Publications discussing the usefulness of naphthalocyanine chromophores in the recording or information layer of optical information media also exist.
For example, U.S. Pat. No. 4,492,750 discloses an ablative infrared-sensitive optical recording composition containing as a component thereof a dispersion of a resinous binder and a soluble naphthalocyanine.
U.S. Pat. No. 4,725,525 discloses the use of various substituted naphthalocyanine compounds, including siloxy substituted naphthalocyanines chromophores, in optical recording media, as does Japanese Kokai No. 177288, published Aug. 8, 1986.
The recording medium, of course, is one of the key elements in any optical recording system, i.e., a system in which the information is recorded or read by light. Such a system would have a usefulness in the storage of audio and video information, data processing and document processing. The commercial viability of an optical recording medium would of course depend upon such technical parameters as the sharpness in recording and playback of the information, i.e., a high signal to noise ratio, as well as the useful life of the information medium. Maintaining the sensitivity of a recording medium throughout the cycles of record-read-erase is also an important consideration.
While dyes or pigments, including naphthalocyanine compounds, have been employed in information storage layers due to their excellent absorption properties, the search for an improved optical information storage medium exhibiting stability and intense absorption at specified wavelengths is continuously ongoing. The search for new and improved naphthalocyanine compounds for use in optical information media, as well as in other optical applications, is also continuously ongoing.
Accordingly, it is a major object of the present invention to provide novel naphthalocyanine chromophores which are useful in optical information media applications.
Another object of the present invention is to provide novel siloxy substituted naphthalocyanines, which are useful in formulating the information layer of an optical information medium.
Yet another object of the present invention is to provide a process for synthesizing siloxy substituted naphthalocyanines.
Still another object of the present invention is to provide a novel optical information medium which contains an information layer comprised of such siloxy substituted naphthalocyanines.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent to those skilled in the art from the following description and the appended claims.